1. Field
The present disclosure relates to tunable circuits, devices and methods. In particular, it relates to tunable artificial dielectrics.
2. Description of Related Art
Artificial dielectrics are known in the art and are made, for example, by distributing small polarizable particles in a uniform background material and represent a macroscopic analogue of a natural dielectrics. The polarizable particles can be either metallic particles or dielectric particles. Reference can be made, for example, to R. E. Collin, “Field Theory of Guided Waves” 2nd Edition, pp. 749-786, IEEE Press, New Jersey, 1990 or W. E. Kock, Metallic Delay Lenses, Bell System Tech. J., Vol. 27, pp. 58-82, 1948. Those two papers are incorporated herein by reference in their entirety.
Known artificial dielectric materials are, for example, discrete or floating metal spheres, disks, strips or rods, etc. When embedding these materials into an electromagnetic field, the artificial particles of these materials are polarized by the applied field, with the positive and negative charges displaced from each other. Each particle then acts as a dipole, contributing to the total charge displacement and thus to an effective dielectric constant.
FIG. 1 shows a plurality of floating metal sheets 1, where the positive and negative charges 2, 3 of each metal sheet are displaced from each other under the influence of an applied field E. The electromagnetic field polarized dipoles act as the artificial dielectrics.
A device based on the artificial dielectrics concept is shown, for example, in W. Andress and D. Ham, “Standing Wave Oscillators Utilizing Wave-Adaptive Tapered Transmission Lines,” Symposium on VLSI Circuits Digest of Technology Papers, pp. 50-53, 2004, where an artificial dielectrics based standing wave oscillator is disclosed.
Further, wavelength or frequency tunability is important for radio frequency (RF), microwave and millimeter wave components and circuits. It can be used to tune the working frequencies of components, such as transmission lines, resonant tanks, antennas, delay lines, filters, inductors, transformers, baluns, duplexers and circuits, such as amplifiers, mixers, filters, VCOs, PLLs and any other circuits that employ wavelength or frequency or tuning filtering.